In 1970, millions of Americans concerned about the environment observed the first “Earth Day.”

In 1983, the West German news magazine Stern announced the discovery of 60 volumes of personal diaries purportedly written by Adolf Hitler; however, the diaries turned out to be a hoax.

In 1994, Richard M. Nixon, the 37th president of the United States, died at a New York hospital four days after suffering a stroke; he was 81.

In 1997, in Peru, government commandos stormed the Japanese ambassador’s residence, ending a 126-day hostage crisis; all 14 Tupac Amaru rebels were killed, all 72 hostages were rescued (one died later of gunshot wounds).

Ten years ago: President George W. Bush announced he would nominate Alan Greenspan for a fifth term as Federal Reserve chairman. Songwriter Felice Bryant, who with her late husband, Boudleaux, wrote “Bye Bye Love” and other Everly Brothers hits, died in Gatlinburg, Tenn., at age 77.

Five years ago: Hillary Rodham Clinton won the Pennsylvania Democratic primary, defeating Barack Obama and keeping her presidential hopes alive. At the close of a two-day North American summit in New Orleans, President George W. Bush chastised U.S. lawmakers for letting international trade deals falter and criticized Democratic presidential contenders for wanting to scrap or amend the vast North American free-trade zone. Singer-songwriter Paul Davis died in Meridian, Miss., a day after turning 60.

One year ago: George Zimmerman was quietly released from a Florida jail on $150,000 bail to await his second-degree murder trial in the fatal shooting of unarmed teen Trayvon Martin. The U.S. and Afghanistan reached a deal on a strategic partnership agreement ensuring that Americans would provide military and financial support to the Afghan people for at least a decade beyond 2014, the deadline for most foreign forces to withdraw. In the first round of the French presidential election, Socialist Francois Hollande narrowly edged conservative incumbent Nicolas Sarkozy, sending the candidates to a May 6 runoff, which Hollande won.